The dominion of vision

If the instinct-driven are primarily driven by impulses that eminate from the amygdala, the ancient core of the brain, the locus of the registry and creation of sound, why does vision, which is lodged in the late-developing temporal lobes, dominate perception. Why do visionaries not think? Why is the thinking of blind people not impaired? Is blindness merely an instrumental disfunction? An optic deficit?